Batteries such as nickel-cadmium batteries and nickel-metal hydride batteries are known as cylindrical batteries. Cylindrical batteries are typically provided with an electrode plate group, obtained by stacking a positive electrode and a negative electrode each in strip form with a separator therebetween for separation, and then spirally winding a stacked body thus obtained. The electrode plate group is housed in a cylindrical battery case made of metal.
Cylindrical batteries as such are highly reliable and capable of easy maintenance, and are used for many purposes such as the power source for cell phones, laptop computers, and the like. In recent years, there is a demand for development of cylindrical batteries suited for high current discharge, as the power source for electrically-assisted bicycles, lawnmowers, electric vehicles, and the like.
Known as a current collecting structure suited for input and output of large currents is, for example, a current collecting structure in which a positive electrode core member and a negative electrode core member protrude from the upper end face and the lower end face of an electrode plate group, respectively, multiple points on the end edge portion of the positive electrode core member are welded to a positive electrode current collector, and multiple points on the end edge portion of the negative electrode core member are welded to a negative electrode current collector.
Further, Patent Literature 1 proposes a negative electrode current collector provided with a plurality of projections. In Patent Literature 1, the negative electrode current collector is disposed between an electrode plate group and the inner bottom face of a battery case, one projection is provided on the center part of the negative electrode current collector positioned correspondingly to the hollow cylindrical portion of the electrode plate group, and a plurality of projections are provided on the area between the center part and the peripheral edge portion of the negative electrode current collector. The plurality of projections protrude from the face of the negative electrode current collector facing the inner bottom face of the battery case, toward the inner bottom face of the battery case. The plurality of projections of the negative electrode current collector are welded to the inner bottom face of the battery case. A negative core member is connected to the face opposite to the face of the negative electrode current collector provided with the projections. In Patent Literature 1, the height of the projection provided on the center part of the negative electrode current collector positioned correspondingly to the hollow cylindrical part is lower than those of the projections provided on other parts of the negative electrode current collector.
[Citation List]
[Patent Literature]
    [PTL 1] Japanese Laid-Open Patent Publication No. 2005-100949